Estimation of Fetal Position and Orientation based on Skeletal Distribution with Robotic Ultrasonography

Since the fetal heart is small and less visible, physicians find it based on the fetal position and orientation assumed with acquired US images. Meanwhile, an artifact due to bones and fetal movement in uterus not only makes the procedure cumbersome but also limits the reliability of diagnosis. Then, this paper proposes the robotic US imaging system allows for the estimation of fetal position and orientation based on the fetal bone distribution which is a key anatomical feature to detect the heart and to avoid the artifact. We obtain intrauterine bone distribution in three dimensions from echo images and estimate the fetal position and abdominal sagittal axis by calculating and analyzing the bone distribution in the entire uterus. The estimation errors in the 3D space were as follows: head position 30.9 ±13.9 mm, pelvis position 16.0 ±2.7 mm, and rotation angle 6.0±7.8
^°
. These results suggest that the proposed method is effective as a technique for estimating the approximate fetal position and has a potential to determine the heart position.